The helmet was made of a single piece of bronze, 27 centuries ago, heated and hammered and annealed by a technique used as late as the Florentine renaissance but now lost forever. It was forged from an alloy of copper and tin, with traces of lead and iron.

The noseguard is a 19th century mix of copper and zinc, probably welded to the helmet after it was unearthed from a temple sanctuary such as at Olympia in Greece. Invisible traces of quartz, calcite, gypsum and feldspar, the dust of its resting place for more than two millennia, cling to the bronze. There has been some corrosion, but that stopped long ago. Known to the Greeks as a Corinthian helmet, it was probably tailor-made for one careful owner in an unknown Greek city state in the 7th century BC. It went into battle with him, protected him from bronze swords and lances, and when he died, in Greek ritual fashion it may well have died with him.

Now high energy probes at British laboratories have brought to life again a story of ancient death and glory. Scientists used the giant synchrotron radiation source at the government's central research laboratory at Daresbury, near Warrington, and the neutron source at the Rutherford Appleton laboratory in Oxfordshire to peer into the fabric and confirm that the noseguard of the helmet was replaced only in the 19th century, identify any corrosion products and measure the alloy metals used in its manufacture.

The findings show the power of state-of-the-art instruments to explore the fine structure of ancient objects without damaging them. Dr John Prag of the Manchester Museum and two physicists, Dr Manolis Pantos at Daresbury and Dr Winfried Kockelmann at Rutherford, have used techniques developed only in the late 20th century on a helmet dating from the world of Herodotus and the heroes of Salamis.

Brad Pitt wears an upmarket version of a Corinthian helmet in the film Troy, released worldwide this week. But Pitt's headgear is a Hollywood anachronism. Achilles and Odysseus wrought their mayhem in a mythical past, and Homer had sung the tale of Troy well before the first Corinthian helmet was hammered out. The helmet takes its name from Corinth, but the style was widely adopted and in use for hundreds of years. On the evidence of vases and coins, Miltiades of Athens donned one for the battle of Marathon and Leonidas the Spartan wore a Corinthian helmet at the battle of Thermopylae.

But the helmet studied in six experiments so far at Daresbury and Didcot was unearthed probably late in the 19th century, and went to the Charterhouse school collection before being sold at Sotheby's two years ago. It is now in the Manchester Museum. It would have been tailor-made for a citizen who had to arm himself at his own expense. The man, a hoplite in his city's military force, would have gone into close combat with a shield on his left arm, his sword arm free, and his head protected by a bronze mask that obscured his vision.

"The whole thing depends on a type of fighting which is almost getting together and shoving," says Prag. "And it doesn't matter that you can't see or hear very much because it really is all happening in front of you or just to one side. It is quite fearsome to look at. You have Darth Vader coming at you.

"Your worry as a museum curator is that it is obviously okay in the ground, because it survived for 2,500 years. If I put it on a display case in damp old Manchester: what is going to happen to it?"

The helmet went to the two laboratories to be subjected to instruments costing hundreds of millions, and the size of city blocks, that can watch washing powder molecules attacking dirt, "see" atoms in action in magnets and measure information storage in compact discs. Pantos wants to use them for the relatively new science of archaeometry.

"Archaeological science is principally materials science, on ancient material, so let's use the same cutting edge techniques on ancient material," he says. "We can do things other techniques cannot, quickly. We have sampled corrosion products from inside the helmet. With a tiny 0.1mm amount we can get the diffraction pattern and therefore the signature of corrosion products in 30 seconds, very accurately. We don't muck about."

The authenticity of the helmet was never in doubt. But the researchers used techniques called neutron diffraction, x-ray diffraction, x-ray fluorescence and infrared spectroscopy to confirm that among other things, the noseguard was not authentic. Alastar Jackson of Manchester University, an authority on bronze armour, had already suggested that the noseguard might be a different alloy mix, since its edges were much sharper than those on the rest of the helmet and its shape was wrong. Pantos says: "It just did not look right. It could have been tested a simpler way. But we went the extra mile, took the extra step, and we haven't finished our work."

"It is much later, because it doesn't work, it is too short, its profile is too vertical," Prag says. "You try putting it on - and Manolis demonstrated this by making a plaster cast - and it bangs on your nose. It needs to stick out because your nose sticks out.

"It suffered in battle. John Prag's point is that this is a cheapo soldier's helmet," says Pantos. "It did not have the thickness of the helmet that Achilles might have used. It does not have that crest on top. It has a fantastic mark at the back that suggests that something sharp went right through the eye, presumably through the head, and very nearly came out through the back. So it has been battered in battle."

The dead soldier's armour would have been stripped from his body by the victors and then set up with other trophies of battle on wooden posts in the sanctuary of Olympia, as offerings to the gods. Armour would be "killed" in a sacrificial ritual, just as a lamb might be.

Prag says: "It happened a lot at Olympia. It stands there for a long time, and either the sanctuary gets too full, or the post rots and it falls down and the Olympic sanctuary guards come along and they gather it all up and they bury it.

"At that point you are committing it to the next world, and you have to kill it. You kill a lamb by cutting its throat, to commit it to the next world, to the gods. You kill a sword by bending it, you kill a helmet by bending the cheek pieces up, and the noseguard up, so that it is dead, it is useless."